Self-extinguishing epoxy resin containing a halogenated polynuclear phenol and a hardening agent



United States Patent Ofiice 3,280,216 Patented Oct. 18, 1986 3,280 216 SELF-EXTINGUISHING E POXY RESIN CONTAIN- ING A HALOGENATED POLYNUCLEAR PHE- NQL AND A HARDENING AGENT Alexander M. Partansky, Concord, Calif., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Apr. 20, 1962, Ser. No. 188,936

15 Claims. (Cl. 260831) The invention relates to an improved epoxy resin com position which is curable to self-extinguishing products having high heat distortion properties and to the method of making such composition and product.

Epoxy resins, broadly, are Well known and widely used. They are prepared, in general, (1) by reacting a halohydrin or epihalohydrin with a polyhydric compound, in the proper molar proportions, in the presence of a suitable catalyst, and dehydrohalogenating the chlorohydrin ether formed to produce substantially a corresponding diglycidyl ether or polyether of the initial polyhydric compound or (2) by reacting a diolefin or polyolefin, which may be cyclic or linear, with a peracid or peroxide to produce substantially a corresponding diepoxide or polyepoxide of the olefin. The epoxy resins so made are liquid or low-melting solids which are readily rendered curable to hard, durable, corrosionand abrasion-resistant resins of the thermoset type by admixing therewith a curing agent selected from either (1) those which coreact, e.g., a primary or secondary amine or a dicarboxylic acid or the anhydride thereof, which enters into a cross-linking reaction with the oxirane groups, and also with the hydroxyl groups of the resin (if present) or (2) a catalyst which effects cross-linking directly between the functional groups of the epoxy resin, e.g., a Lewi acid such as BF and organic complexes thereof, or a tertiary amine.

The cured resinous composition of the invention is selfextinguishing and exhibits high strength and thermal prop erties, a hereinafter more fully explained. It is well suited for casting, impregnating, encapsulating, laminating, and surface coating. It is made by a procedure which offers economic and technical advantages.

In the practice of the invention an epoxy resin, of the type prepared by reacting a polynuclear phenolic compound, having an average hydroxyl functionality greater than 2, with an epithalohydrin in the presence of an alkali metal hydroxide, is reacted with a specified molar proportion of a halogenated polynuclear phenol or mixture thereof, having an average hydroxyl functionality of at least 2, in the presence of a curing agent which may be either the catalytic type, e.g., a Lewis acid, an organic complex thereof, or a tertiary amine or a hardening agent of a co-reactant type, e.g., a dicarboxylic acid anhydride or a polyfunctional aliphatic or aromatic primary or secondary amine.

A method of preparing an epoxy resin of the type required for the practice of the invention is set out hereinafter.

As used herein, the term, polyphenol, denotes a polynuclear phenolic compound having either two, or an average of more than two, hydroxyphenyl groups per molecule. The term, halogenated polynuclear phenol, as used herein, denotes such polyphenolic compound having ring-attached bromine and/or chlorine. Other substituents, as hereinafter explained, may also be present on the hydroxyphenyl groups. The term, self-extinguishing, means not burning in the absence of an igniting source, i.e., the capacity of extinguishing any burning of itself in the absence of an exterior igniting source under the conditions defined by A.S.T.M. standard test D645-56T. S.E. herein means self-extinguishing.

The halogenated polynuclear phenolic compound may be any brominated and/or chlorinated phenolic compound containing at least 2 phenolic rings, e.g., any of the bisphenols or relatively low molecular weight novolacs containing sufiicient bromine and/ or chlorine substituents to impart self-extinguishing properties to the cured resinous composition.

The additional curing agents which are employed with the halogenated phenol to convert the epoxy novolac to a curable composition to give a highly cross-linked cured product may, as aforesaid, be either of the catalytic or the co-reactant type. Illustrative of suitable curing agents are tertiary amines such as benzyldimethyl amine, Lewis acids (and particularly amine complexes thereof such as BF :monoethylamine), dicarboxylic acid anhydrides such as maleic, phthalic, succinic, hexahydrophthalic, and polycarboxylic acid anhydrides such as pyromellitic di- =anhydride, methylamino-alkyl substituted aminophenols such as tridimethylaminomethyl phenol known as DMP- 30, l-cyanoguanidine (usually referred to as dicyandiamide or DiCY), and amides prepared by reacting dimerized or trimerized unsaturated fatty acids and a polyamide of which the Versamids are illustrative.

The manner of preparing the resin of the invention is best illustrated by the following general procedure:

The epoxylated polyphenol, e.g., an epoxy novolac, a halogenated binuclear or higher polyphenol, e.g., brominated or chlorinated 4,4-isopropylidenediphenol, and a catalyst or co-reactant (as hereinafter more fully described) are admixed in a suitable vess'el, preferably provided with heating, temperature control, and stirring means. When an auxiliary fire-retardant agent is desired, e.g., antimony oxide, it is admixed with the above reaction mixture at this time. A preferred mode of preparing the resin is to charge the vessel with the epoxylated polyphenol, heat it to a fluid condition, e.g., about C., and promptly admix therewith the. halogenated polyphenol and the catalyst or co-reactant (and thereafter the auxiliary fire-retardant agent, if desired). When the mixture is substantially homogeneous, it is cast or applied as a coating, impregnant, or the like and the thus cast, coated, or impregnated article subjected to an elevated temperature of between about C. and about 210 C. for a time sufiicient to effect a cure thereof to a hard durable resin composition. The time required for cure varies with the specific reactants and curing conditions employed.

The proportion of the halogenated polyphenol, as above defined, to the epoxy resin, as above defined, is such that between about 0.1 and about 0.45 equivalent weight of phenolic hydroxyl groups is provided by the halogenated polyphenol per equivalent weight of oxirane groups of the epoxy resin; preferably the proportion is between about 0.12 and about 0.3 equivalent weight of phenolic hydroxyls per equivalent weight of oxirane groups. The halogenated polyphenol must provide enough halogen to impart the desired self-extinguishing properties to the cured resin product. This has been found in the absence of any auxiliary S.E. components to require that the resinous composition contain at least about 10% bromine or at least about 18% chlorine or an intermediate value therebetween when both brominated and chlorinated polyhydroxy phenols are employed. Such intermediate minimum value is calculable and increases in direct proportion to the weight percent ratio of chlorinated phenol to brominated phenol employed. The minimum number of hydrogen atoms on each molecule of polyhydroxy phenol required to be substituted by bromine and/or chlorine is determined for a given phenol-epoxy resin reaction mixture by the halogen requirement for a selfextinguishing resin, as above explained.

Since not more than 0.45 phenol hydroxyl equivalent weight per oxirane equivalent weight is employed, at

least half of the initial oxirane groups are available for reaction with a supplemental curing or hardening agent. The purpose of the supplemental agent is to complete cross-linking between the oxirane groups. The amount of supplemental curing or hardening agent added, therefore, varies depending not only upon the particular agent and the curing conditions employed, but also upon the proportion of phenolic hydroxyl equivalents provided by the halogenated phenol per oxirane equivalent in the reaction mixture.

When the curing agent is a catalytic type, e.g., BF -MEA, between about 0.5% and based on weight of the reaction mixture, is employed. When the curing agent is a co-reactant type, e.g., a primary or secondary polyamine or a dicarboxylic acid anhydride, the amount employed is usually calculated to supply a total of between about 0.8 and 1 times the stoichiometric quantity of curing agents necessary to react with the oxirane groups. To illustrate, a primary diamine (having two amino groups per molecule) is employed in an amount which provides about one-quarter or slightly less than one-quarter mole thereof for each equivalent Weight of the oxiran'e groups in excess of those required to react with the halogenated polyphenol, whereas when a dicarboxylic acid anhydride is employed it is added in an amount which provides about one mole or slightly less than one mole thereof per equivalent weight of oxirane groups (present in excess of those required to react with the halogenated phenol present).

The invention may be practiced by admixing all the ingredients and casting the resulting mixture into a mold contoured to produce a desired shaped casting and allowing the thus cast mixture to set, at between about 100 and 210 C., preferably between about 140 C. and 200 C. for a time suflicient for the curing reaction to be substantially complete, about 2 to 24 hours usually conveniently being employed.

The resulting mixture may also be employed directly as a coating, encapsulating, impregnating, or laminating resin.

Alternatively, the final mixture may be partially prereacted in some applications. For example, in the preparation of pro-impregnated laminating materials a partial cure may be effected prior to the final assembly and curing of a laminated structure. It will be seen that the invention is useful in meeting diver needs employing a resinous composition and is applicable to a variety of manufacturing operations for which an epoxy type resin is desirable, possessing (in addition to desirable strength, flexibility, adhesion, and wearand corrosionresistant properties) self-extinguishing and high heat distortion properties.

In one embodiment of the invention, a supplemental fire-retardant additament may be employed. Among such ad'ditaments are antimony-, boron-, anr phosphorus-containing materials, including pigments. The supplemental additaments may be employed up to about but the beneficial effect does not appear to be augmented by employing more than about 5%. When such additaments are employed in an amount to provide between about 2% and 5% by weight of the resin, the minimum amount of the bromine and/or chlorine required in the final resin may be lessened. For example, when the additament is antimony trioxide, the halogen requirements are reduced to about 6% by Weight of bromine or about 10% by weight of chlorine, or a calculable intermediate percent when both brominated and chlorinated polyphenols are employed. Antimony oxide is the preferred supplemental fire-retardant additament to employ in the practice of the invention.

In one embodiment of the invention, only enough of the halogenated polyphenol is employed to provide the required amount of phenol ring-attached bromine or chlorine to impart self-extinguishing properties to the subsequently cured resin composition, and other dior polyhydroxy phenolic compounds, having an average hydroxyl functionality of at least 2, are employed as a supplemental hydroxyl source to make up the maximum permissible overall proportion, i.e., not over 0.45 and preferably not over about 0.3 equivalent weight of phenolic hydroxyl groups per equivalent weight of oxirane groups of the epoxy resin. The novolac resins are particularly suitable for use as the nonhalogenated polyhydroxy phenol compound to employ.

The novolac resins (sometimes called merely novolacs), accordingly, may be employed in the practice of the invention, either or both as (1) the polyphenol which is epoxylated to prepare the epoxy resin (having an oxirane functionality of greater than two as required by the invention) or (2) upon halogenation, as the halogenated polyphenol, (either singly or in admixture with other halogenated or nonhalo genated polyphenols having an hydroxyl functionality of at least 2) to provide not more than a total of 0.45 equivalent Weight of hydroxyl groups per equivalent weight of said oxirane groups in the epoxy resin in the practice of the invention. The novolac resins employed for use as either (1) or (2) above, in the examples hereinafter set out, were prepared by reacting a molar excess of phenol with formaldehyde in the presence of an acid catalyst and may be considered to have the formula:

OH OH OH 1 r l I R a l n R in R R wherein It may vary from an average greater than zero to about 4. In the practice of the invention, n usually has an average value of from about 0.5 to 3.5, making the usual average total number of phenol groups per molecule from about 2.5 to 5.5. R and R substituents are selected from the group consisting of hydrogen, chlorine, bromine, alkyl, aryl, aralkyl, and alkaryl hydrocarbons, at least a minimum of which, as aforesaid, must be bromine or chlorine. To provide such substituted novolac, a corresponding substituted phenol may be employed as the phenolic reactant with the formaldehyde in making the novolac. However, in preparing brominated novolac it is preferred to start with a non-brominated phenol and to brominate the novolac formed in the reaction with formaldehyde. Novolac resins are thermoplastic and, accordingly, may be remelted and employed in further re actions.

A novolac resin of the type above described may be epoxylated by any one of a number of known procedures, typically by reacting it with epichlorohydrin in the presence of an alkali metal hydroxide. The amounts of each reactant employed are such as to provide between 3 and 5 chemical equivalent weights of oxirane groups of the epichlorohydrin and an excess of about 5 percent chemical equivalent weight of the alkali metal hydroxide, per equivalent weight of hydroxyl groups present in the novolac. The temperature employed may be from about 40 to 150 C. but is usually between about 70 and C. Usually, the novolac resin is dissolved in epi chlorohydrin in a suitable reaction vessel and a 25-50 percent aqueous solution of NaOH or KOH is added thereto, usually over a period from 0.1 to 4 hours, accompanied by mild agitation. The reaction is exothermic and usually a reflux condenser with a separating type receiver is employed to aid in maintaining the desired temperature and to remove the excessive amount of water added with the caustic as well as that formed in the reaction. A partial vacuum may be used, if it is desirable to employ a temperature below the boiling point of epichlorohydrin. An epoxy novolac is thus produced which is subsequently separated from by-product salt formed in thereaction and from excess epichlorohydrin by con- 2 t 6 ventional procedures, e.g., separating the salt by filtra- Reference to Table I shows that the Lewis acid type tion and removing the excess epichlorohydrin by vacuum catalyst, as illustrated by BF adducted with monoethyl distillation. The resin may then also be water-washed amine, gives the higher heat distortion temperature values. and dried. Further reference to the table also shows that as the equiva- The epoxy novolac for use in the practice of the invenlent ratio of hydroxyl groups to oxirane groups increases, tion is assumed to have the formula: the heat distortion temperature decreases when either the (|)CHz-CHCH2 O-OH2-CH-CH2 (I)-CHzOH-C H2 I I 01. m 01. y

l R LR R' in a n wherein n has the same value and R and R represent the Lewis acid or tertiary amine is employed. From 0.1 to same substituents as denoted in the novolac formula, supra. 0.2 equivalent weight of hydroxyl to oxirane groups ap- To illustrate modes of practicing the invention and to pears preferable, as illustrated by Examples 3 to 7 and 16 show the presence of the desirably high strength and therto 18, when BF :MEA is employed as a supplemental mal properties in castings, as demonstrated by the high curing agent within such ratio range, in contrast to the heat distortion temperature and Barcol hardness values use of a larger equivalent ratio of hydroxyl to oxirane obtained, a series of examples illustrative thereof was cargroups, as illustrated by Examples 8 to 10 and 19 to 21.

ried out. The procedure followed was substantially that The compositions of Examples 10, 12, 15, 21 and 23, set out hereinabove. The epoxylated polyphenol employed wherein a ratio of 0.4 equivalent weight of hydroxyl to was an epoxy novolac having an average oxirane funcoxirane groups was employed, had substantially lower tionality of between 3.2 and 3.4. The halogenated polyheat distortion temperatures, illustrative of the results obphenol was tetrabromobisphenol A. The co-react-ant or tained as the ratio of equivalents approaches the 0.45 catalyst was varied in the different examples. In some maximum ratio of the invention. The Barcol hardness examples, Sb O was added as a supplemental fire-revalues show that satisfactory hardness is obtained by varytardant. The specific co-reactant or catalyst and the ing ratios of hydroxyl to oxirane groups within the pracamounts of all reactants, expressed in parts by weight per tim of the invention.

100 parts of the epoxy novolac resin, are set out in Table r comp rative purposes, castings were made fol- I. Castings, /2" x /2" x 6" in size, were then made by lowing various procedures which were not in accordance pouring the various compositions in molds which had been with the invention. They are designated Runs A to L. preheated to about 80 C. and heating the molds contain- R ns A and B employed the same epoxy novolac as ing the compositions for the times and at the temperatures the examples above, but p y as the Polynuclear set out in Table I. The castings so made were then tested phenylhydroxy compound (instead of tetrabromobisfor heat distortion temperature and Barcol hardness. The phenol A) a novolac resin having an average molecular test results are also shown in Table I. weight of 320 and average OH functionality per mole- TABLE I.CASTINGS MADE ACCORDING TO THE INVENTION EMPLOYING AN EPOXY NOVOLAC,TETRA- BROMOBISPHENOL A. AND EITHER A CATALYTIC OR CO-REACTANT TYPE OF CURING AGENT Tetrabromo- Catalyst or (Jo-reactant I p bisphenol A Hardener S11 0: Percent Example added in Bromine Curing H.D.1., Barcol No. percent of in Resin- Schedule, C. Hardness Equivatotal hardener C./Hrs. PER 1 lent Kind PH R mixture Ratio 2 4 i 1 2o. 5 .134 ,1}? g 1%}: 9. 9 180/18 195 44 2 20. 5 134 0. 2 None 9.7 180/18 144 39 3. 16. 2 107 3. 5 None 8. 0 150/2-1-180/16 204 46 4- 16. 2 107 3. 5 2. 0 8. 0 150/2+180/16 202 49 5- 21.1 3. 6 None 10. 0 /2+180/16 198 48 6- 21. 1 .140 3. 6 2.0 10. 0 150/2-1-180/16 200 49 7- 26. 4 175 3.8 None 12. 0 150/2-1-180/16 183 48 8 35. 3 233 4. 0 None 15. 0 150/2+180/16 161 47 9 45. 3 .300 4. 3 None 18. 4 150/2+180/16 47 10 60. 4 400 4. 0 None 221- 150/2+180/16 146 46 11 21.1 140 2.0 None 10. 0 150/2+180/16 147 36 1 60. 4 400 2. 0 None 22. 1 150/2+180/16 143 34 13 21. l 140 2. 0 2. 4 10.0 l50l2+180ll6 V 161 40 14.- 35. 3 233 2.0 2. 7 15.0 150/2+180/16 156 38 15 60. 4 .400 2. 0 3. 2 22.1 150/2+180/16 145 89 I6 16. 2 .107 BF3-MEA 3. 5 None 8. 0 150/2-1-180/4 203 50 17 21. 1 140 BFa-MEA 3.6 None 10. 0 150/2+180/4 195 49 18 26. 4 BF3-MEA 3. 8 None 12.0 150/2+180/4 181 50 19-- 35. 3 233 BF3-MEA 4.0 None 15.0 150/2+180/4 167 49 20 45. 3 .300 BFa-MEA 4. 3 None 18.4 150/2-1-180/4 152 49 21 60.4 400 B Fa-IVIEA 4. 0 None 22.1 150/2+180/4 138 22 21. 1 140 BZDMA 2. 0 None 0 150/2+180/4 129 36 23 60. 4 400 BZDMA 2. 0 None 22. 1 150/2+180/4 123 34 MNA 63. 9 24 33. 6 .222 BZDMA 0 82 1. 66 12. 0 /18 168 44 25 27. 9 8' V 1. 66 12. 0 180/18 161 46 26 19.3 .128 MDA 22.6 2. 0 8. 0 9 R+180l18 173 44 1 PER is parts by weight of hydroxy compound or catalyst per 100 parts of epoxy novolac resin having an average oxirane functionality per molecule 013.2.

2 Equivalent ratio refers to hydroxyl groups to oxirane groups present.

3 H.D.1. is heat distortion temperature according to A.S.I.M Test D. 648-56.

4 BF -MEA is a 48/52 adduct of boron trifluoride with monoethylamine.

5 DiCY is dicyandiamide.

BzDMA is benzyldirnethylarnine.

' MNA is methyl nadic anhydride.

8 MA is maleic anhydride.

P B, when it appears, means that the resin-phenol-hardener mixture was precured at room temperature (about 25 C.) overnight (about 16 hours) before being heated.

MDA is 4,4-methy1cue dianiline.

7 cule of 3.2, (which are satisfactory reactants) but were employed in an amount which is provided a ratio of hydroxyl to oxirane groups of about 1, in contrast to the permissible maximum ratio of not over 0.45, of the in- S The invention was further illustrated by examples wherein glass cloth laminates were prepared in accordance therewith. These examples employed a brominated polyphenol selected from brominated bis-phenol A, brovention. BF -monoethylamine catalyst was employed 5 minated novolacs, and mixtures thereof with epoxy as in the examples of Table I. Runs C to H employed novolacs in amounts to provide a proportion of between the same epoxy novolac as in the examples but employed 0.109 and 0.270 hydroxyl equivalent weights per oxi- (as the polynuclear phenylhydroxy compound) both rane equivalent weight in the presence of sufficient catatetrabrominated bisphenol A and the novolac resin lyst or c-o-reactant supplemental curing agent. The comof Runs A- and B to give a ratio of total hydroxyl to ponents of the resulting curable mixtures are shown oxirane groups of greater than the 0.45 maximum ratio in Table III. The mixtures so made were then admixed of the invention. The supplemental non-phenolic curing with acetone to make 55% to 60% by weight total solids or hardening agents employed were as shown in Table solution-s having a viscosity of between about 35 and 40 II. centipoises.

Runs I and J employed, as the epoxy resin, the di- Glass cloth, known as 181Volan A, having an averglycidyl ether of bisphenol A (instead of the epoxy age thickness of 0.0085 inch, an average weight per novolac employed in the previous examples ond runs). square yard of 8.9 ounces, and a breaking strength of It had an average oxirane functionality of between about 350 pounds per inch, which had previously been treated 1.9 and 1.95. The hydroxyl compound employed was with a chromate to enhance resin adhesion thereto, was the novolac resin employed above. The amounts emcut into strips 6 feet long and 10 inches wide. The ployed r id d a ti f equivalent weight of hydroxyl strips were drawn through the acetone resin solution per equivalent weight of oxirane groups of about 1. and the excess solution removed therefrom by passing BF -monoethylamine was the supplemental curing agent the strips between doctor rolls. The thus resin-treated used. The results of the comparative runs are set out strips were hung up for from 14 to 16 hours at room in Table II below, temperature (about 25 C.) to evaporate the solvent and TAB LE II Hydroxyl Compound Catalyst 2 Curing Comparative Run Percent Schedule, H.D.T., Barcol Designation Ratio of Bromine CJHrs. O. Hardness Kind PHR 1 Equiv- Kind PER alents A 3.2 Novolac 57.6 1.00 BFg-MEA 0.1 None 18074 113 38 B 3.2 Novolae 57.6 1.00 BFg-NlEA 1.0 None 18074 96 43 C Tetrabromobisphenol A.-." 47.0 .307 BzDMA 1.8 15.1 R+180l18 132 38 Novolao 33. 7 580 Total .887

D Tetrabromobisphenol A... 38.0 .248 BzDMA 1.8 12.6 lid-180118 138 37 Novolae 38. 0 642 Total .890

E Tetrabromobisphenol A"-.. 30.1 .196 BzDMA 1.7 10.3 R-i-180/13 145 37 Novolac 10. 4 694 Total .890

F TetrabrornobisphenolA 22.8 .150 BzDMA 1.6 8.2 ."B.}-180/18 145 37.

Novolao 40. 2 690 Total .840

G TetrabromobisphenolA 38.0 .248 Tetramethyl 1.8 12.6 R+180l18 135 38 Novolac 37. 4 642 Guanidine.

Total .890

H Tetrabromobisphenol A 23.9 .156 DiCY 3.0 9.8 180/18 155 N ovolac 16. 6 293 Total .449

14 Novnlar' 59.0 1.00 BZDMA 1.0 None 180/4 s7 34 J'4 Ngvnlm' 59.0 1.00 BzDMA 0.1 None 1s014 s1 40 1 Parts by Weight of hydroxyl compound or catalyst per hundred parts 4 In Runs I and J the epoxy resin employed was a commercial diglycidyl of the epoxy resin. ether of Bisphenol A, known as DER 332, instead of the epoxy novolao 2 See footnotes of Table I for full names of catalysts. used in other examples. 3 Where R appears it means that; the resin-phenol-hardener mixture was preoured at room temperature (about 25 C.) overnight (about 16 hours) before being heated.

Reference to Table II shows that, as the ratio of then precured for about 5 minutes at 125 C. in an equivalent weights of hydroxyl groups provided by the oven. The strips were then cut into 10" x 10" squares polynuclear phenol to the equivalent weights of oxirane and laminated into a l2-ply laminar structure according groups increases in excess of the 0.45 maximum of the to conventional nesting procedure. The 12 ply asinvention, the heat distortion temperature becomes insembly was then placed in a heat-controlled press becreasingly less satisfactory. It also shows that an even lower and less satisfactory heat distortion temperature is obtained when a difunctional epoxy resin, e.g., D.E.R. 332 (rather than an epoxy resin having an oxirane functionality greater-than 2) is used.

tween platens at sufiicient pressure to bring the components of the laminar structures into firm mutual contact, and given a first cure at 150 C. for about 5 minutes; the laminate was then placed under a pressure 7 5 of p.s.i. and further cured at about C. for from 17 to 30 minutes. The pressure was then released and the laminar structures were post-cured in an oven for 2 hours at 150 C. followed by 4 hours at 180 C. The percent of increase in weight of the Volan A glass cloth due to impregnated resin was about 35%. The laminates so made were then tested for flexural strength and modulus at both room temperature (about 25 C.) and either at 127 C. (260 F.) or about 149 C. (300 F.). 4-ply laminates were prepared in like manner and tested for self-extinguishment.

For comparative purposes, a laminate was also prepared employing hexachloroendomethylenetetrahydrophthalic anhydride (known as HET or chlorendic anhydride) as an S.E. curing agent instead of the brominated polyphenolic compound required by the invention. This run is designated Comparative Run K of Table I11.

10 Resistance to solvents was also determined on the laminates of Examples 33 and 34 and Comparative Run L. The tests were run by weighing 1" x 3" x A of the laminates, immersing them in various solvents for meas- 5 ured periods of time, and removing, drying by blotting TABLE III Brominated Polyphenoi Catalyst or supplemental coreactant Inter- Example hardening agent Per- Percent laminal N 0. OH HDT cent Resin in Flcxural Modu- Flexural Mo dushear,

Kind PH R 1 equiva- Wt. Laminate strength, lus, strength, lus, p.s.i.

lents Br p.s.i. p.s.i. p.s.i. p.s.i.

per Kind 4 PH R oxirane 27 Tetrabrtliniobis- 27. 3 179 BF -MEA..- 3 182 12. 6 36. 2 80, 500 3. 41 '66, 500 3.14 2, 700

pneno 28 do 16. 7 109 BF MEA 3 203 8. 4 38.8 78, 900 3. 00 '63, 600 2. 87 2, 360 29 Ngf gla: with 31. 6 270 BF -MEA-.- 2 175 12. 2 44. 1 78, 700 2. 71 59, 100 2. 26 2, 720

r. d 31. 6 270 4 12. 2 47. 1 71, 600 2. 45 52, 700 2. 02 2, 820 25. 0 214 2 203 10. 2 41. 5 85, 600 2. 76 66, 600 2. 39 2, 680 25. 0 214 4 10. 2 46. 9 75, 700 2. 66 56, 800 2. 16 3, 220 Comparative Run K HET 81111. 100 480 226 43. 2 86, 300 2. 96 24, 200 1. 01 4, 000

1 Between 22 and 25 C. 302 11; 260 F. except where asterisk appears when temperature was 1 Pit-1R means Parts (by Weight) per 100 parts of epoxy novolac. 4 See footnotes of Table I for full descriptive terms for catalysts. f Whcnd dicyandiamide was used, it was first dissolved in diethyl orniami e.

Reference to Table III shows that laminates made with the resin composition of the invention had a flexural strength of not less than 75,700 p.s.i. at room temperature and not less than 52,700 at 260 F. Laminates employing 3% by weight of BF .monoethylamine as a catalyst showed not less than 63,600 psi. at 300 F. Although the run employing HET anhydride (Run K) had good flexural strength when tested at room temperature, this value fell 011 to the low figure of 24,200 psi. when tested at 260 F. 4-ply laminates, prepared from the same impregnated cloth as the laminates set out in Table HI, and tested according to A.S.T.M Test D 135-56T were found to be self-extinguishing. Comparative Run K, however, although self-extinguishing as noted above, was unsatisfactory for the reason of low strength at elevated temperature.

1 "SkydroY is an aeroplane brake fluid, comprising essentially dipropylene glycol.

2 The laminate of comparative run L employed DiCY-cured epoxy novolac resin DEN 438; it had no self extinguishing property.

3 Laminate compositions in examples 33 and 34 were identical with those in examples 27 and 28 described in Table III.

1 HET is hexachloroendomethylenetetrahydrophtahlie anhydride now widely used as a halogenated curing agent for 8.1). epoxy resin compositions.

1 In examples 27 and 28 elevated temperature tests were conducted at 300 F. instead 01 260 F.

B 28% Cl.

polynuclear phenolic compound having an oxirane functionality per molecule of more than 2, a halogenated polynuclear phenolic compound having an average hydroxyl functionality per molecule of at least 2, in an amount sufficient to provide an equivalent weight ratio of hydroxyl to oxirane groups of between about 0.1 and about 0.45 and, a supplemental hardening agent in an amount sufficient to eifect cross-linking of substantially all the remaining oxirane groups, said halogenated polynuclear polyphenolic compound providing suflicient halogen to render the subsequently cured resin composition self-extinguishing.

2. The resin composition of claim 1 wherein the glycidyl ether of a polynuclear polyphenolic compound is an epoxy novolac having an average oxirane functionality of between about 2.5 and about 5.5.

3. The resin composition of claim 1 wherein the halogenated polynuclear phenolic compound is a brominated isopropylidenediphenol employed in an amount sufficient to provide at least about 10 percent bromine, by weight of the resulting curable mixture.

4. The resin composition of claim 1 wherein the halogenated polynuclear phenolic compound is a chlorinated isopropylidenediphenol in an amount sufiicient to provide at least about 18 percent chlorine by weight of the resulting curable mixture.

5. The resin composition of claim 1 wherein the halogenated polynuclear phenolic compound is a novolac resin having an average hydroxyl functionality per molecule of between about 2.2 and about 6.0.

6. The resin composition of claim 1 wherein the selfextinguishing properties imparted to said resin are supplemented by an inorganic additament, in an amount of between about 0.5 and about 5.0 percent by weight of said resin, selected from the class consisting of compounds of boron, phosphorous, and antimony.

7. The resin composition of claim 1 wherein the supplemental hardening agent is a Lewis acid.

8. The resin composition of claim 7 wherein the Lewis acid is a BF -rnonoethanol amine complex present in an amount of between about 0.5 and about 5.0 weight percent of the composition.

9. The resin composition of claim 1 wherein the supplemental hardening agent is diciandiamide in an amount of between about 0.5 and about 5.0 weight percent.

10. The hard durable self-extinguishing epoxy resin consisting essentially of the composition of claim 1 after being subsequently subjected to heat at a temperature between about 100 and about 210 C. for from about 2 to about 24 hours.

11. The method of curing an epoxy resin containing an average of more than 2 oxirane groups per molecule consisting of admixing therewith a halogenated polynuclear phenolic compound containing at least 2 hydroxyl groups per molecule to provide a ratio of between about 0.1 and about 0.45 .hydroxyl equivalent weights to oxirane equivalent weights, and a supplemental hardening agent selected from the class consisting of primary, secondary, and tertiary aliphatic and aromatic amines and mixtures thereof, Lewis acids and organic complexes thereof, and dicarboxylic acids and anhydrides thereot in sufiicient amount to eifect cross-linking among remaining oxirane groups and subjecting the resulting reaction mixture to a temperature between about 100 and about 210 C. until substantially all the oxirane groups present have reacted to provide a strong, hard, durable epoxy-type resin having a high heat distortion value, resistance to burning, and resistance to chemical attack.

12. The method according to claim 11 wherein the epoxy resin is an epoxy novolac, the halogenated polynuclear polyphenolic compound is selected from the class consisting of brominated binuclear phenolic compounds and brominated low molecular weight phenolic novolac resins and containing suflicient bromine atoms to render the subsequently hardened resin self-extinguishing according to A.S.T:M. Test D -56T, and the supplemental hardening agentis a Lewis acid in an amount between about 0.5 and about 5.0 percent of the reaction mixture.

13. The cured resin made according to the process of claim 12.

i 14. A flexible strong and durable laminated structure having high heat distortion temperature and fire-retardant properties consisting essentially of glass cloth laminae impregnated with and adhered together by the resin composition of claim 10.

15. The resin composition according to claim 1 Wherein the halogenated polynuclear phenolic compound is present in an amount sufficient to provide a molar ratio there-of to the oxirane groups of between 0.1 and 0.3.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Skeist, Epoxy Resins, N.Y., Reinhold, 1958. E6 S52.

Rubber and Plastic Age, May 1956 (page 290 relied on).

MURRAY TILLMAN, Primary Examiner.

LEON I. BERCOVITZ, Examiner.

E. J. TROJNAR, P. LIEBER MAN, Assistant Examiners. 

1. AN EPOXY RESIN COMPOSITION CURABLE TO A SELF-EXTINGUISHING PRODUCT HAVING A HIGH HEAT DISTORTION TEMPERATURE, HARDNESS, AND CHEMICAL RESITANCE, CONSISTING ESSENTIALLY OF THE REACTION PRODUCT OF A GLYCIDYL ETHER OF A POLYNUCLEAR PHENOLIC COMPOUND HAVING AN OXIRANE FUNCTIONALITY PER MOLECULE OF MORE THAN 2, A HALOGENATED POLYNUCLEAR PHENOLIC COMPOUND HAVING AN AVERAGE HYDROXYL FUNCTIONALITY PER MOLECULE OF AT LEAST 2, IN AN AMOUNT SUFFICIENT TO PROVIDE AN EQUIVALENT WEIGHT RATIO OF HYDROXYL TO OXIRANE GROUPS OF BETWEEN ABOUT 0.1 AND ABIUT 0.45 AND, A SUPPLEMENTAL HARDENING AGENT IN AN AMOUNT SUFFICIENT TO EFFECT CROSS-LINKING OF SUBSTANTIALLY ALL THE REMAINING OXIRANE GROUPS SAID HALOGENATED POLYNUCLEAR POLYPHENOLIC COMPOUND PROVIDING SUFFICIENT HALOGEN TO RENDER THE SUBSEQUENTLY CURED RESIN COMPOSITION SELF-EXTINGUISHING. 